I have a very similar problem, only mine is leaking on the front manifold and its the exhaust port all the way to the right on the front. My 91 toronado leaked in the same spot. I think ive heard about the manifolds warping so that may be the problem. I plan on fixing mine this summer sometime. I got a new front manifold that is in excellent shape with only 15k miles on it so hopefully that fixes my problem, but yours sounds similar.... best thing you can do is pull em off and check em out. Good luck.
1995 Bonneville SSEi:
(still without a motor and tranny) 15.606 @ 87.95mph (stock)
1998 Regal GS:
DHP 1.0, JMB FWI, ZZP 3" DP, 04 GP 12" Brakes, ZZP 180° Drilled T-Stat, SLP Single Outlet Catback, Silverstars